In the PTR patch notes it says "Players can now craft multiple items of gems at a time within the same tier, so long as they possess the necessary materials" and I was wondering effects this will have on the prices of gems and tombs.

Personally I think that Radiant Star gem prices are going to drop a lot. With Radiant Stars now easy to craft, why would people pay for others to do it for them. With that being said, I believe that Flawless Squares will get a price bump and tombs as well.

Does anyone else have any insights?

I don't think we'll be able to separate out any effect from craft all and new patch release. Flawless Square gems are already up 10-20% just on the PTR notes release.

The only difference it will make in the AH is that there won't be any 0-4% premium for crafting gems anymore. RS gems will likely be under their mat price for a while, if not permanently. I don't think anyone was trying to make money off of them, anyway.

I think this will benefit the user rather than the seller, unless of course there is still arbitrage between the two AH's.

I, for one, would much rather craft my own than buy them from the AH. The only thing that was keeping me from doing it before (crafting) was the sheer time investment involved in making your own...